1. Technical Field
The present disclosure relates to an organic light emitting display device, and more particularly, to an active organic light emitting display device.
2. Discussion of the Related Art
Recently, with the development of information society, lightweight and thin flat panel displays have been actively developed. Examples of such flat panel displays include liquid crystal displays and organic light emitting display devices. Since the organic light emitting display device does not require a separate light source such as a backlight used in the liquid crystal display and has excellent color reproduction, the organic light emitting display device realizes thinner and clearer picture quality.
Among such organic light emitting display devices, an active organic light emitting display device generally includes unit pixels comprising three sub-pixels for each of red, green, and blue light. Each sub-pixel is defined by a crossing between a gate line and a data line, and is driven independently by a driving circuit that includes a separate thin film transistor (TFT).
Various conductive lines including a thin film transistor are arranged in the driving circuit of the sub-pixel. The conductive lines include a gate line, a data line and a power line are arranged in the periphery of the sub-pixel. The gate line, the data line and the power line respectively supply a gate signal, a data signal and a power signal, which are required for driving the sub-pixel. If the conductive lines reflect external light, external visibility is deteriorated.
In order to prevent such reflection of external light from occurring, a polarizing plate may be used. If the polarizing plate is used, 45% or less of the light emitted from the organic light emitting device is transmitted through the polarizing plate, resulting in a luminance reduction of 50% or more. But, if driving power is increased to compensate for the reduced luminance, then the lifespan of the organic light emitting layer gets reduced.
Particularly, in case of a transparent organic light emitting display device that has recently received much attention as a display for the next generation, a transparent area is arranged such that light from a rear background may be transmitted to the front of the display device. This results in a degradation of external visibility and contrast ratio.
Moreover, in transparent organic light emitting display devices, since a polarizing plate is often eliminated for improved light transmittance of the transparent area, an alternative solution for improving external visibility and contrast ratio is required.